1. Field of the Invention
The present invention relates to an inkjet recording head, which is capable of incorporation into information equipment such as a word processor, facsimile, and printer, a method for manufacturing the same, and an inkjet recording device. In particular, the present invention relates to an inkjet recording head configured to allow high-density arrangement in a two-dimensional array of piezoelectric elements and facilitate mass production thereof, a method for manufacturing such an ink-jet recording head, and an inkjet recording device having such an inkjet recording head.
2. Description of the Related Art
In recent years, an impact recording process has attracted much attention for its small noise in recording and a high recording speed thereof. Among other impact recording processes, an inkjet recording process used in inkjet printers has been in wide use. The inkjet printer allows ink droplets to be ejected from the recording head and attached onto recording paper so that characters, figures and photographs are printed at a high speed. The inkjet printer is capable of recording the images onto plain paper without using a special fixation processing. According to a known inkjet recording process called drop-on-demand inkjet recording scheme, an electro-mechanical transducer such as a piezoelectric actuator is used to generate pressure waves (acoustic waves) in pressure chambers filled with ink, thereby allowing ink droplets to be ejected from the nozzles disposed in communication with the pressure chambers.
An inkjet recording head using the drop-on-demand ink-jet scheme is described in JP Patent Publication No. Sho 56-64877. FIGS. 1A to 1C show the conventional inkjet recording head described in the publication. FIG. 1A is a longitudinal sectional view of the essential parts of the inkjet recording head, FIG. 1B a partially-broken top plan view thereof, and FIG. 1C a sectional view taken along the line c—c of FIG. 1B.
The inkjet recording head described in the publication has a base plate 44 and a diaphragm 42 which are coupled together to form a plurality of pressure chambers 45 therebetween. An ink nozzle, or orifice 43, is formed at one end of each pressure chamber 45. A plurality of rectangular piezoelectric elements 41 are mounted on the diaphragm 42 corresponding to the respective, pressure chambers 45. The piezoelectric elements 41 are electrically connected to a pulse generator 40. The pressure chamber 45 is supplied with ink from an ink reservoir 47 through an ink supply tube 46. The piezoelectric elements 41 are made of piezoelectric ceramic, and more particularly, PZT (lead zirconate titanate).
In the conventional inkjet recording head as described above, the piezoelectric elements 41 are manufactured by machining a piezoelectric ceramic plate to configure predetermined size and shape. Examples of he method for machining the piezoelectric elements 41 with high precision include a dicing saw technique such as for cutting or trenching by using the rotation of a disc containing diamond particles (dicing blade), and a wire saw technique. These high-precision machining methods for piezoelectric elements, although suited to linear machining, are incapable of working the piezoelectric ceramic plate (piezoelectric plate) into arbitrary shapes.
An example of a manufacturing method for forming a piezoelectric plate into an arbitrary shape is described in JP Patent Laid-Open Publication No. Hei 11-207970. The manufacturing method described in this publication is as follows. Initially, a sheet of foaming agent is bonded onto a dummy glass plate, and a piezoelectric film is laminated thereon. A resist is applied thereon and patterned for mask portions. Thereafter, the piezoelectric film is subjected to cutting by sandblasting at regions other than those covered by the mask portions. Subsequently, the resist is removed. The resultant piezoelectric plates are subjected to positioning onto the ink reservoirs and placed on a conductive film formed on the diaphragm before the dummy glass plate is removed. Then, electrodes are mounted on the piezoelectric film to obtain the inkjet recording head. Using the manufacturing method described in the publication, the piezoelectric film can be formed into arbitrary shapes according to the mask pattern.
In the field of the inkjet recording heads, such an ink-jet recording head having a two-dimensional array of a number of nozzles (hereinafter, this type of the inkjet recording head is referred to as a matrix head) is expected as the next-generation head in view of the high-density nozzle arrangement with suppressed increase in the head size. The technique described in the publication relates to an inkjet recording head having a plurality of piezoelectric elements arranged only in one dimension. It is silent as to the provision of a number of piezoelectric elements arranged in a two dimensional array at a high density to form a matrix head.